(1) Field of the Invention
This invention pertains to capacitors, particularly to tantalum capacitors having a non-contiguous arrangement of cathode elements.
(2) Description of Related Art
Tantalum capacitors are highly regarded for their electrical and physical characteristics. Typical wet tantalum capacitors have porous anodes which are housed in a tantalum case and hermetically sealed. Such capacitors are well suited for use in military and industrial circuits that demand quality and reliability in filtering, bypass, coupling, storage and timing applications. They are designed for reliable service over the temperature range of -55.degree. C. to +125.degree. C., and therefore meet the needs of the avionics and aerospace industry.
Among the premium capacitors of this type are the PuriTan.TM. capacitors available from Tansitor Electronics Inc., Bennington, Vt. Due to their superior ripple capabilities, PuriTan.TM. capacitors are exceptionally well suited for filtering in switching regulator applications, an area where conventional wets are not normally used, due to the relative high ripple current ratings required.
These capacitors are usually fabricated by inserting a preformed cylinder of tantalum into a tantalum can. The cylinder serves as the cathode in the completed device. A tantalum anode, electrolyte, and suitable sealing and connecting means complete the construction. For many applications, however, it is not necessary to have as much cathode capacitance as is provided by the full cathode cylinder, particularly in view of the high cost of tantalum. An obvious solution to this problem is to form a thinner cathode cylinder. Unfortunately, thin cylinders of tantalum are very difficult to both make and handle. Losses due to breakage more than compensate for any savings expected from the use of thinner cylinders.
There remains, then, a need for a tantalum capacitor in which the cathode capacitance can be tailored to meet the needs of the user, and yet can be fabricated on existing equipment and in conventional forms for use by the industry.